Wind, solar and diesel: Let the numbers tell you the story

Prof. Paul Wessels, owner of Southwest Windpower’s Whisper 200 (1 KW) and Whisper 500 (3.2 KW) wind turbines, provided the Company his complete system metrics. The two turbines are components of a larger hybrid system that is completed with solar and diesel. The energy produced by the system powers Wessels’ rural off-grid cattle farm. The data is broken down by each component of his system, as described in our case study from a previous blog post. Prof. Wessels, who keeps meticulous data records, monitors his off-grid system year round; however, the table consists of specifics from each season in South Africa, which is comprised of mid-summer, mid-spring and mid-winter through the months of January, April, July and October 2010 respectively.

Component

Annual Energy Ah

Annual Energy kWh

Diesel offset: Liters

Diesel offset: Gallons

Savings USD

CO2 offset: kg

CO2 offset: lbs

Whisper 200

29,604

1066

507

134

$741

1167

2599

Whisper 500

39,396

1418

675

178

$986

1553

3459

Solar PV

177,204

6379

3038

802

$4,435

6987

15,558

Diesel

14,100

508

-

-

-

-

-

TOTAL

260,304

9,371

4,221

1,114

$6,162

9,707

21,616

SOUTH AFRICA’S GEOGRAPHY

Generally speaking, there is more sun per year in South Africa than there is wind. The ratio of sun to wind in Bloemfontein, central South Africa, varies substantially due to its central location.

South Africa has a Mediterranean climate that consists of mild temperatures with dry and warm summers. January is typically the hottest month of the year, subsequently making July the coldest. Sunlight consumes some 68 percent of the day. The approximate 32 percent that remain is likely to be cloudy, shady or low sun intensity. Most wind is received along the coastal regions, exceeding some 3,760 kWh. The estimated annual wind speed for the country when measured at 10m (32 ft) high is 6 m/s (13.4 mph). The Western Cape, Northern Cape, Eastern Cape and KwaZulu-Natal receive the most amount of wind. The further inland, the less wind. Prof. Wessels’ cattle farm is situated in the central part of the country, where much lower wind speeds are typical.
To estimate how much diesel use was prevented using wind turbines and solar panels, we assumed the average cost of diesel in South Africa at approximately $1.46 USD per liter (as it was at the time of this writing). His complete renewable system offsets the emissions of about 9.707 kg or 21,616 lbs of carbon per year! He saves an approximate $6,100 USD a year. This does not take into consideration the cost of maintaining the diesel generator or the transport of the fuel to his remote location.

NUMBERS SOMETIMES SPEAK LOUDER THAN WORDS

This one example of many where the numbers tell the story and prove that a hybrid-system, one of which consists of a combination of multiple energy sources, is extremely beneficial not only for the environment, but also to your energy budget. Take a look for yourself and let the figures persuade you to begin improving or installing your renewable energy system today!